Wednesday, October 27, 2021

United Trifold: Handlepost Upgrade

As you may already know, I like to modify my bikes, to make it suit my requirements. The United Trifold bike is no exception.

From the start, I had already planned to upgrade the handlepost, due to various reasons. Although the stock handlepost works well, I did not like the purple colour. It just does not look good in my opinion, although others may have a different opinion. The purple frame is fine for me, but not the long handlepost with a big purple shaft.

Upon receiving the bike, another reason I wanted to upgrade was to lower the height of the handlebar. As on my other folding bikes, I tend to use a short handlepost, as I want the handlebar height to be lower for a more sporty riding position. From the Dahon Boardwalk to the Fnhon DB11, I have always been using shorter-than-average handleposts.

I do not like high handlebars that force me to sit upright and pedal, as it feels very inefficient. I guess I prefer the sporty riding position of drop bars, which I am very used to.

Before changing to a new handlepost, let's check out the stock handlepost first.

Stock purple handlepost on the United Trifold. I was surprised to see a double bolt clamp at the handlepost base!

Most handleposts we see on Dahon-style folding bikes have a handlepost with just a single bolt at the base, which means a shorter clamping height. The downside of this design is lower handlepost stiffness, as the handlepost only clamps onto the steerer tube with a short section.

I first saw the double bolt design on Tern Physis handleposts, which are highly rated for the incredible stiffness and strength. I know this in detail as I have installed the Tern Physis 3D handlepost on the Dahon Boardwalk. Lots more details there if you would like to know more.

This means that the stock handlepost on the United Trifold is actually of a good design, having a tall base to improve the handlepost stiffness. However, the length is still too much for me, so I need a shorter handlepost.

However, it is very hard to find a double bolt handlepost to replace the stock handlepost! I first came across the double bolt Fnhon handleposts when I was building the Fnhon DB11, but they are hard to find nowadays. Apparently, the cost of production for these 3D forged handleposts is too high, and the production has been discontinued. It is a pity as they are really good handleposts, with high stiffness, low weight and nice appearance with no welds.

Why can't I use a single bolt handlepost to replace the stock double bolt handlepost? Because with a shorter clamping section on the single bolt handlepost, the steerer tube would be too long. I can add a  thick spacer under the handlepost to solve this, but the handlepost stiffness would still be poorer.

Weight of stock United Trifold handlepost is 783 grams. This is considered heavy. Imagine if your road bike has a stem that weighs 700+ grams instead of 100+ grams!

After much searching on Taobao, I finally found a double bolt Fnhon handlepost, which is from existing stock. Basically once its gone, they won't be making any more of it. It is twice as expensive as the conventional single bolt type, but it is well worth the money. Just look at the pictures below, and also from the previous comparison when I was building the Fnhon DB11.

New handlepost in sandblasted matte black

Double bolt clamp at the base! Even the bolts and hardware are black in colour.

Weighs 657 grams, quite a lot lighter than the stock handlepost.

New handlepost is 39 cm in length, while the stock handlepost is 42 cm in length. Just a 3 cm difference.

I wanted an even shorter handlepost, such as 35 or 37 cm, but they are not available. Therefore, this new handlepost is only 3 cm shorter than the stock one. A small difference but hopefully noticeable.

Both are double bolt clamp designs, as can be seen from the tall base.

Fnhon handlepost has a red coloured button to release the safety catch, while the stock handlepost has a sliding latch. Both are nice.

Position of clamps are different. Fnhon handlepost has the bolts at the side, while the purple handlepost has the bolts directly under the clamp. Not sure if there is any actual difference in function.

Here is the main difference. Fnhon handlepost is 3D forged as one piece with no welds at the joint, unlike the other one.

Handlebar clamp designs are almost the same. Both open up fully if you need to insert a curved or riser handlebar.

Not exactly the same, but close enough.

Internal clamp design is different. The Fnhon design has the handlepost fully hollow, without a "wall" like the purple handlepost.

The guide for the shaft/bolt are located at different positions. I'm not sure if there is any noticeable difference in quality, strength or durability. Probably just a different way of achieving the same function.

Upon closer look, they are quite different internally. Same clamp concept, but different layout.

As seen earlier, the slot for the double bolt clamping are located differently.

The handlepost should be a straight swap, since both are double bolt types with a tall base. By swapping, the handlebar height will be lowered by 3 cm. I would have preferred a lower handlebar height, but I can't find a shorter double bolt handlepost.

However, before I installed the new handlepost, I decided to study the headset first. I was checking if there is a possibility to change to a better headset, as the stock headset looks quite inferior. Check out the details in the next post.

Friday, October 22, 2021

United Trifold: Single Speed Freehub Modification

This is the first time I am setting up a single speed drivetrain, so some things are new for me. For example, since there will only be one speed on the United Trifold, I need to choose the gear ratio wisely. My planned usage would be to just use this bike for leisure rides, mostly on pavement and park connectors. This means that it should be a comfortable gear ratio that is most suited to a comfortable cadence of 80-90 RPM, at a speed of 20-25 km/h.

If the gear ratio is too low, I will spin out too easily at cruising speeds. On the other hand, if the gear ratio is too high, it will be tough to start off from a stand still, and even normal slopes will be too difficult.

Based on my experience riding the Focus Paralane all-weather road bike, I usually move off in the 6th gear, which has a gear inch of about 57. Then, I would cruise leisurely in gear 7 and 8, which are 64 and 72 gear inches respectively.

Therefore, I will aim for a single speed gear range of perhaps around 60-65 gear inches, since I need to find an ideal balance for my own riding style and fitness. It will neither be a fast bike nor a climbing bike. Note that everyone will have different preferences, so you need to try and decide for yourself, and not just follow others because it works for them.

I have already decided to use a 52T Stone chain ring on this United Trifold, so I just need to decide the sprocket size to use.

Table shows the gear inches if different chain ring and sprocket sizes are used. Based on a 52T chain ring, I can use either a 13T or 14T sprocket to get the gear inches that I want.

With a cadence of 80-90 RPM, a 13T sprocket will give a speed of 25-28 km/h. A 14T sprocket will give a speed of 23-26 km/h.

I decided to try the more relaxed gearing first, which is with the 52T chain ring and 14T sprocket. This will give a gear inch of 59.4 and a speed of 23-26 km/h, at a cadence of 80-90 RPM.

Coincidentally, the single speed gear ratio that I have chosen corresponds exactly to gear 5 on the stock United Trifold 7 speed internal hub setup. By the way, I think the stock gear range is well chosen with a suitable low and top gearing.

Although you can technically use any 14T sprocket from a cassette, the sprockets on a multi-speed cassette have shorter teeth to facilitate shifting. This may cause chain drop, especially if the chain line is not ideal. Also, sprockets from a cassette are thinner, which means less durability, although it is not a concern for me. The concern is that thinner sprockets are more likely to gouge aluminium freehub bodies, especially if you use that sprocket 100% of the time. There is even more stress if you stand up to pedal when going up slopes, since you can't spin smoothly up slopes when there is only a single speed.

I decided to get a dedicated single speed 14T sprocket, since it is not expensive anyway. As shown below, the gear teeth are tall and thick, although it still fits 11 speed chains. This type has an internal spline shape that matches standard Shimano freehub bodies.

14T single speed sprocket weighs 26 grams.

Chain is able to enter the inner width of the 11 speed chain, although there is not much free play.

11 speed chain is able to rest fully on the sprocket teeth. The tall teeth improves chain engagement.

Next, I need to place the sprocket somewhere along the freehub body, to best match the chain line of the front chain ring. This means that I need a lot of freehub spacers to clamp the single speed sprocket on the freehub body. This is not so easy, as there are a couple of requirements for the spacers.

1) Spacers should allow fine adjustment steps to best align the chain line with the front chain ring.
2) Spacers + sprocket need to stack up to a height just beyond the thread on the freehub body.
Too short, and the lock ring will bottom out on the freehub body.
Too tall, and the thread engagement will be reduced, which might strip the threads on the freehub body.

I bought a set of spacers from Taobao, which are specifically designed for single speed conversions like mine. However, I doubt that the spacer heights and chain line will be perfect, as there are just 3 spacers, which does not allow for fine position adjustments.

Set of spacers and lock ring for single speed conversion using standard freehub bodies.

The lock ring in this conversion kit has a larger flange (right side), but for what purpose?

The flange on the cassette lock ring (left) has a smaller flange diameter, as it needs clearance with the chain when it rests on the small 11T sprocket.

A lock ring for single speed conversion will rest on the spacer instead, which has a larger diameter. The flange diameter thus needs to be larger to rest properly on the spacer.

Next comes the trial and error process of choosing the appropriate spacer heights and best chain line position. This United Trifold frame that I have (unlucky or applies to all?) is quite warped, so I think any measurements are not useful, best to just try it out.

The trial and error process basically involves choosing the spacers that allow the lock ring to be tightened correctly (without bottoming out, and with maximum thread engagement). Then, arrange the sprocket among the spacers to align the chain line with the front chain ring. A straight chain line is the best for efficiency and chain retention. This involves repeated lock ring tightening and loosening, and repeated installation and removal of the rear wheel from the frame. Repeat this process until all the requirements are satisfied.

Final spacer arrangement and sprocket position, with a chain line that looks best aligned to the front chain ring.

I used an aluminium spacer just under the lock ring, to prevent damaging the resin spacers during lock ring tightening. This is the ideal chain line and spacer stack, for future reference.

With the ideal spacer stack established, I weighed them to enable accurate weight tracking for the bike.

Another view of the single speed setup (bike is shown upside down), before installing the chain tensioner.

It was fun to calculate and choose the appropriate single speed gear ratio for this United Trifold. Whether it is appropriate or not will need to be tested, once the whole bike is assembled. If the gear ratio is too high or too low, I can always change to a larger or smaller sprocket.

Wednesday, October 20, 2021

United Trifold: Chain Tensioner Upgrade

Even though I am converting the United Trifold from the stock 7 speed internal hub to a simple single speed drivetrain, I will still need a chain tensioner to manage the chain.

The chain tensioner is needed to ensure that the chain does not become slack during riding, or during folding. For standard derailleur drivetrains, the cage of the rear derailleur acts as the chain tensioner to manage the chain.

I already have the new front single crankset, and also a brand new wheelset for conversion. I can actually use the same stock chain tensioner that came with the bike, since the function is the same. Upgrading to aftermarket chain tensioners will not modify or affect the function, except the aesthetics.

Stock chain tensioner, made almost entirely of plastic, is about 186 grams. This looks almost the same as the Brompton type.

On the Brompton M6R which I had previously, I did not change the stock chain tensioner. It was not a component that I felt needed to be upgraded, unlike other parts such as the hinge clamps, Ezy wheels or grips.

Back of stock chain tensioner. This squarish profile matches with the shape of the rear dropout area.

However, I soon found that the stock chain tensioner could not be used with 11 speed chains, as the pulley teeth are too wide. They are suitable for single speed or 7/8 speed chains, but not 11 speed chains. I wanted to use an 11 speed chain because it will then be similar to my other bikes, plus it will be a bit lighter as well. Also, a narrower 11 speed chain will fit better on the narrow wide chain ring to prevent chain drop.

Therefore, I had no choice but to change to an aftermarket chain tensioner. Most of them look the same, regardless of the brand Litepro or others. There are a few different designs by H&H and other boutique Brompton brands, but those are quite rare and much more expensive.

In my case, for a single speed drivetrain, I basically only need the chain tensioning function. The sliding pulley is not necessary to perform shifting, unlike on multi-speed Bromptons with a few external sprockets.

Litepro chain tensioner, made of aluminium but with many thin and hollowed out sections. Weighs only 129 grams, quite a lot lighter than the stock resin chain tensioner.

At this point, I am not sure if the chain tensioner will fit without any modifications or not. I have heard that if you change to this Litepro chain tensioner with the stock 7 speed internal hub, the chain line of the internal hub sprocket and the chain tensioner does not match up, causing chain drop issues.

While studying the United Trifold, I found that the rear hub OLD (Over Locknut Distance) is quite strange. The Nexus Inter-7 hub has an OLD of 130 mm, but when I measured the bare frame, I found that the frame OLD is 135 mm.

When assembled, the axle nuts on both sides are used to squeeze the rear triangle, so that the frame is compressed to make the 135 mm OLD frame clamp the 130 mm OLD hub. This is a bad design, as the frame is deformed quite a lot.

I believe that United makes all the Trifold bikes with a rear OLD of 135 mm, to suit all their different models of 5 speed, 7 speed and 11 speed drivetrains. Since the Alfine 11 speed hub has an OLD of 135 mm, all other specifications will just have to use the same frame, even though they are technically not compatible.

Since most rim brake wheels have a rear OLD of 130 mm, there will be a 5 mm difference in hub width. I can get a rim brake wheelset with a 135 mm OLD rear hub (disc brake hub), but it will not be of the special spoke lacing design which I wanted.

As I will change the rear hub fixing method from nutted type to quick release type, it is not possible to compress the frame with a QR axle. It is not strong enough to do that, nor is it safe to apply so much stress on the QR axle.

Therefore, I need to increase the rear hub OLD from 130 mm to 135 mm. From my prior experience modifying the Dahon Boardwalk and Dahon Vitesse, I knew that there is a hub adapter than can do exactly this.

Hub adapter that is fixed onto the end of the hub, to extend it by 5 mm.

This end of the adapter is placed over the rear hub axle.

Weighs just 3 grams, which is insignificant.

This hub adapter can be placed on either the drive side or the non-drive side, to increase the OLD from 130 to 135 mm.

Normally, it will be placed on the non-drive side, so as not to affect the position of the cassette relative to the rear derailleur hanger. In my case, since it is just a single speed sprocket, either the drive or non-drive side is OK.

Hub adapter placed on the non-drive side of the hub (bike is shown upside down).

After adding the hub adapter, the OLD of the hub fits snugly into the rear triangle. There is some clamping effect, as the hub OLD is a bit wider than the opening of the frame. This is OK as it helps retain the wheel inside the frame, after I remove the QR axle.

Now, the next part is the secret to converting the rear hub from nutted type to QR type. Remember that even with a QR axle, I will still need to add the chain tensioner. The original position of the chain tensioner is to be clamped on the outside of the frame, using a second nut.

However, I have never seen a QR axle with a chain tensioner added on top of it. How will it be done?

My idea is to use a long QR axle, and use a second QR nut to clamp both the chain tensioner and the frame against the rear hub to secure them.

This is the first QR nut, which will clamp the rear hub lightly inside the frame.

A long QR axle is needed, which gives me enough thread length to put on a second QR nut later. This QR axle is from a MTB wheelset which requires a longer QR axle.

Steel QR axle for the rear wheel weighs 65 grams

Lightweight titanium QR axle for the front wheel is just 22 grams.

After placing the first QR nut on the QR axle, the chain tensioner is then placed over it. When the QR lever is closed, this first QR nut should only clamp the frame lightly. The majority of the clamping force should come from the second QR nut, which will be located on the outside of the chain tensioner.

I had to select a small QR nut, so that the chain tensioner can go over it. This QR nut also acts to help centralize the chain tensioner on the QR axle, replacing the original nut on the 7 speed internal hub axle.

Placing the chain tensioner over the first QR nut. The nut needs to be small and short enough, so that it does not protrude from the chain tensioner.

Finally, use the original large washer, together with a second QR nut to secure the chain tensioner on the frame.

The first QR nut (hidden inside) needs to be set so that it only lightly touches the frame when the QR lever is closed. The second QR nut (shown outside) needs to be tight, so that when the QR lever is closed, it clamps the chain tensioner and also the frame strongly against the hub axle.

This setup works surprisingly well, and allows the chain tensioner to be added to a conventional QR axle.

An alternative way would be to just use one QR nut on the inside. This QR nut would be set to clamp strongly against the frame. Then, after adding the chain tensioner, use a M5 nut or something similar to clamp the chain tensioner against the frame, using the thread of the QR axle. This allows the chain tensioner to be removed without loosening the QR axle. However, a tool is also needed to make sure that the M5 nut can secure the chain tensioner to the frame without it self-loosening.

With this chain tensioner change and QR axle setup, the bike is ready for a front single speed drivetrain! The next step would be to determine the position of the single rear sprocket, to best match the chain line of the front chain ring.

Saturday, October 16, 2021

Focus Paralane: All-Weather Usage

For casual riding, you would normally only go cycling when the weather is good, which is defined as not raining. Most people avoid riding in the rain, or even after rain, as the wet roads will make the bike very dirty, due to the water and dirt that is splashed up onto the bike and the rider.

However, if you are commuting to work by bike, you don't always have the luxury to choose when to ride. If you choose not to ride home that day (due to rain or wet roads), it means that the next day or next time you commute to work, you will not be able to ride, as the bike is still stuck at the office.

This was why I had a dedicated commuting bike, which uses belt drive, internal hub, disc brakes, mudguards and other rain proof designs to ensure that I can commute regularly even when it is raining or if the roads are wet. The Avanti Inc 3 was first, followed by the Fabike C3 which is lighter in weight.

Then, once I realized that a good rust resistant chain is available, it opens up the possibilities as I can just use a regular road bike with mudguards as my all-weather commuting bike. The Focus Paralane is set up just like a road bike, but with additional mudguards.

Thus, I get an all-weather road bike that rides fast and is not afraid of rain or wet roads, which allows me to commute regardless of weather. Of course, when there is heavy rain, I will still be unable to ride, but that is because of the low visibility and slippery roads, rather than a bike limitation.

Here are some pictures of the Focus Paralane, going through wet roads and getting splashed with water and dirt, just like an all-weather commuting bike.

No one else on the wet park connector, as it is just after rain.

Wet roads? No problem!

With full mudguards and a host of rust resistant components, riding on wet roads is not a problem for me, even at road bike speeds.

At West Coast Park, with oil rig construction in the background.

Good for exploration, as I don't need to worry about getting the components dirty.

How it looks after wet rides, and this is with mudguards. It would be a lot worse without mudguards.

These components are pretty much rust proof with respect to rain water. Dirty but still perfectly functional.

With a large 11-36T cassette and a 40T chain ring, the Focus Paralane can even make it up Jalan Dermawan, one of the steepest slopes in the west.

This is not a camera trick, it really is this steep. Just look at the fence and the bike resting against it.

I'm surprised to see cars at the top of the slope, as it seems quite challenging to drive up and down this steep slope safely.

Good challenge for those who likes climbs. This is a short but steep slope.

I'm really happy with this all-weather road bike, and I can go out for a ride without worrying that I will get caught in the rain. For me, getting wet in the rain is not the issue. Rather, it is the work needed to clean up the bike after a wet ride, to prevent rust.